It is proposed to modify a compound, which was previously synthesized and shown to be a reversible oxygen carrier, in such a way as to allow it to be tested as an oxygen carrying substitute for hemoglobin. Another synthetic route to similar compounds is under development. BIBLIOGRAPHIC REFERENCES: (1) "Condensation of Tetraaldehydes with Pyrrole. Direct Synthesis of "Capped" Porphyrins", by Joseph Almog, Jack E. Baldwin, Robert L. Dyer, Mary Peters, J. Amer. Chem. Soc., 97, 226 (1975). (2) "Reversible Oxygenation and Autoxidation of a "Capped" Prophyrin Iron (II) Complex", by Joseph Almog, Jack E. Baldwin, Joel Huff, J. Amer. Chem. Soc., 97, 227 (1975).